This invention relates to a wireless communication terminal configured to selectively transmit data on a plurality of routes.
In recent years, expectations are rising for Internet-of-Things (IoT) services in which automatic recognition, automatic control, remote measurement, and the like are executed through connection to the Internet from, and communication between, various “things” that are not computers or other information/communication devices but have a communication function. As one mode of such IoT services, automobiles or other mobile objects with a wireless communication device installed therein function as mobile communication terminals to transmit/receive data to/from a cloud (servers and storage apparatus). Telecommunication carriers provide metered-rate wireless communication services intended for this mode of IoT services that use an existing wide-coverage cellular network.
Use cases of IoT services of the mode described above include one in which a mobile communication terminal transmits sensing data and the like to the cloud in real time, and is controlled by the cloud based on a result of analysis of the data. For example, in a remote control service where sequential images obtained by a camera that is installed in an automobile are transmitted to the cloud, and an operator on the cloud side uses the sequential images to determine how the automobile is to be controlled, the transmitted images need to reach the cloud with a one-way delay that is on the order of several ten milliseconds because the environment surrounding the automobile changes moment by moment. One of technologies that fulfill this requirement is multi-root communication, which uses a plurality of routes (for example, communication systems run by different telecommunication carriers) to transmit copies of the same data, and in which the receiver side identifies and discards a redundant packet. Use of a plurality of different telecommunication carriers simultaneously and receiving data in the order of arrival on the receiver side guarantees communication with a small delay. However, this manner of communication, which always uses a plurality of different telecommunication carriers simultaneously, increases the amount of communication data and raises communication cost. To avoid those problems, multi-root control technology is needed, which selects a plurality of wireless communication systems for use in data transmission only when necessary.
Examples of the related art for selecting communication systems to be used from among a plurality of options include JP 2000-174770 A, JP 2015-95870 A, and JP 2001-36585 A.
In JP 2000-174770 A, there is disclosed a wireless data communication apparatus configured to conduct wireless data communication with the use of a plurality of lines by multi-linking. The wireless data communication apparatus includes a stabilizing unit configured to select lines by switching data paths based on monitoring information that is obtained from the monitoring of states of lines.
In JP 2015-95870 A, there is disclosed a communication apparatus including: buffer information collecting means for collecting transmission buffer information, which indicates the amount of transmission data accumulated in a transmission buffer of a mobile station; throughput information collecting means for collecting transmission throughput information, which indicates the transmission data rate of the mobile station; a communication information database for storing, as communication information, the transmission buffer information and the transmission throughput information in association with information on a time and a train position at which the transmission buffer information and the transmission throughput information have been collected; and transmission data sorting means for sorting, when data is received from a user terminal on the train, for transmission, the data into mobile stations based on at least two pieces of communication information that are associated with a time and a train position at which the data has been received.
In JP 2001-36585 A, there is disclosed a communication system in which a transmission unit of a transmission-side terminal transmits data bound to a reception-side terminal to a gateway transmission apparatus, a reception unit of the gateway transmission apparatus receives the data bound to the reception-side terminal, a selection unit of the gateway transmission apparatus selects one of a plurality of communication paths, and a transmission unit of the gateway transmission apparatus transmits the data bound to the reception-side terminal over the selected communication path to a gateway reception apparatus. When selecting a communication path, the selection unit takes into account the amount of data to be transmitted, the usage amount of a transmission buffer associated with a communication path, the line speed of an access zone, and a transmission delay time that is measured or otherwise obtained and stored in advance. The reception unit of the gateway reception apparatus receives the data bound to the reception-side terminal, and the transmission unit of the gateway reception apparatus transmits to the reception-side terminal the data bound to the reception-side terminal. In a case where it is necessary to take into account the order of the data bound to the reception-side terminal, the data is put into order by suspending the transmission of the data bound to the reception-side terminal as needed. A reception unit of the reception-side terminal receives the data bound to the reception-side terminal.